Abstract: The renewable energy sources had been known to humankind since the very beginning of the human civilization, though practiced in very primitive forms. The first civilization and subsequent greater civilizations, came up, existed, and flourished at or near river valley/basins. Rivers provided water for irrigation, domestic utilization, transportation; overall development of the entire civilization. In the latter years, the increase in the human population and certain revolutionary inventions and discoveries like fire, the wheel, and domestication of cattle and animals led the movement and spread of the human populations in the other parts of the globe far from river irrigated lands. Humans learnt to utilize underground waters and harvest rainwater for living and survival. In the course of development, there also increased demand for more energy and its storage so that it can be utilized as and when required. This brought humankind to discover the laws of thermodynamics, emergence of combustion engines, electromagnetic induction, electricity and storage devices, such as batteries and supercapacitors. The development has been revolutionized since last few centuries with increasing demand of energy with growing industries and a faster life. Nowadays, because of massive exploitation of fossil resources for fuel and electricity, and concerns of global warming, exploring renewable energy alternatives are gaining momentum. Of many renewable resources, viz., sun, wind, water, geothermal, biomass, etc., the biomass energy is the most widely studied one in terms of both, published literature and wide social acceptance across the globe followed by solar and wind energy.The chapter presents the potential alternatives to non-renewable energy resources, mechanism and machinery to draw and exploit the energy in the usable or utilizable form; past, present, recent progresses and future scope of the ongoing researches on this subject. The chapter also deals with the relative merits or pros and cons of the massive and large scale installation of machinery to produce electricity from some of the noteworthy renewable energy resources, such as, wind, water and sun, which is affecting the local environment or natural habitats, flora and fauna; overall influence on the delicate balance of the ecosystem.

Abstract: Worldwide, developing countries struggle to overcome numerous problems that constrain their socio-economic development. Sub-Saharan African countries represent a good example of developing countries with serious developmental challenges. Thus, this chapter presents a critical analysis on the socio-economic situation in Sub-Saharan Africa and the links between limited access to modern energy services and the prevailing socio-economic circumstance. It discusses the expected roles of renewable energy technologies in increasing energy access in the region and highlights important factors that influence extensive deployment of renewable energy technologies for sustainable development. Reliable statistical data on both the Human Development Index (HDI) and Energy Development Index (EDI) rankings indicate that most countries in Sub-Saharan Africa lie far below the world average and as a region, Sub-Saharan Africa scores least. There is high level of poverty and inadequate social services, which is attributed to acute shortage of modern energy services. In Sub-Saharan Africa, over 70% of the population lack reliable access to electricity and modern cooking fuels, which represents a large proportion of the „energy poor‟ in the world. Lack of access to modern energy services limits economic and agricultural opportunities, negatively affects the environment, promotes gender inequality and constrains delivery of social services such as health care delivery system and education. Thus, one of the biggest developmental challenges in Sub-Saharan Africa is to find effective and pragmatic solutions for increasing energy access. Sub-Saharan Africa is richly endowed with renewable energy resources such as biomass, wind, solar, hydropower and geothermal, which largely remain unexploited. The renewable energy resources are widely available throughout the region unlike the conventional fossil-based resources, that is, coal, oil and gas, which are concentrated within very few countries. Therefore, the renewable energy resources if properly and fully utilized can provide clean, affordable and reliable energy services that will promote socio-economic activities and support sustainable development.

Abstract: Nanocomposites containing inorganic semiconductor nanomaterials are of tremendous interest for low-cost 3rd generation solar cells. A variety of possible materials and structures could be potentially used to reduce processing costs which is highly attractive for large scale production of solar cells. Controlling the morphology and surface chemistry of nanomaterials remains a key challenge that has major knock-on effects in devices. Herein, an attempt is made to highlight some of the challenges and the possible solutions for depositing high quality thin film composites for solar cell devices.

Abstract: In recent decades, due to some urgent and unavoidable issues, such as increasing energy demand, climate change, global warming, etc., the R&D of renewable energies have become inevitable to pave way the sustainable development of human society. In this regard, solar power is widely considered as the most appealing clean energy since there is no other one being as abundant as the sun. The amount of solar energy reaching our earth within one hour equals to the total annual energy need of all of humankind. Since the energy resources on Earth are being exhausted, solar energy have to serve as the main energy source in coming century and beyond. The photovoltaic solar cells developed so far have been based on silicon wafers, with this dominance likely to continue well into the future. The surge in manufacturing volume as well as emerging technologies over the last decade has resulted in greatly decreased costs. Therefore, several companies are now well below the USD 1 W−1 module manufacturing cost benchmark that was once regarded as the lowest possible with this technology. Thin-film silicon, such as hydrogenated amorphous silicon (a-Si), microcrystalline silicon (mc-Si) and related alloys, are promising materials for very low-cost solar cells. Here in this article, a brief description of thin film solar cell technologies followed by deferent state-of-art tools used for characterizing such solar cells are explored. Since characteristics of thin-film solar cells are the main ingredient in defining efficiency, the inherent properties are also mentioned alongside the characterizations.

Abstract: Hydrogenated amorphous silicon (a-Si:H) has been developed as an important materials in thin film-based photovoltaic technologies because of considerable cost reduction as a result of low material consumption and low-temperature process. Among the materials used for thin film solar cells, amorphous silicon is the most important material in the commercial production. Despite of these benefits, the efficiency limit for a single band gap thin film based solar cell predicted by Shockley and Queisser (i.e. ~31%) has become a matter of challenge for current research community. Considering the thermodynamic behavior of a single threshold absorber in generating electricity from solar irradiance, this limit seems inevitable, and thus a tremendous investigation is now being carried out in different dimensions such as hot carrier generation, rainbow solar cell, multiple exciton generation, multiband absorber etc. Nonetheless, so far reported efficiency (ηlab~12%) provide enough room to improve and take challenge to reach to the highest value for a-Si:H based solar cell design. Further to improve architectural design as well as engineer the materials, it is indispensable to understand the optical, electrical and structural properties of aSi:H as an active layer. Here in this article, an attempt was taken into account to focus on such characteristics that affect the overall cell efficiency.

Abstract: One of the most matured solar thermal technology commercially been used today is the solar parabolic trough power plants. With many challenges for solar photovoltaic technology to improve beyond its current efficiency levels, solar thermal technology is getting importance. A parabolic trough power plant works on an average temperature of about 400 °C. Although, there are some recent advances to increase the working temperature, power plants are not completely equipped in other parts of the system to handle such high temperatures. Hence, there is an imbalance in the achievements reached in different research areas of this technology. This article focus on this technology from its birth to current market competitions, including an overview of recent research advancements.

Abstract: Water desalination is receiving increasing attention due to water scarcity in many places in the world. Although two third of the earth is covered with water, most of this water is salty (97.5%) and therefore not suitable for human, animal or plant needs. Furthermore, most of the fresh water available throughout the work is not accessible such as icebergs and some deep ground water. Water uneven distribution throughout the world creates another problem of water scarcities in arid places. Africa and Middle East are having the smallest share of natural, pure water resources. Fortunately, these areas of arid climate and low fresh water are rich in the most significant renewable energy source, solar energy.
In this chapter, the potential of the utilization of renewable energy sources is discussed. Several desalination techniques that can be powered by renewable energy are discussed. Those techniques include the non-conventional ones such as the solar stills, humidification dehumidification desalination and membrane distillation. What is common within all of these techniques is the relatively low temperatures needed to operate the plants (around 80 °C) that can be afforded easily using solar collectors for heating water (and sometimes air). Several layouts of humidification dehumidification systems and membrane distillation system are also discussed in details taking into consideration the improvement of performance due to energy recovery systems and the recent trends of such technologies. Although the solar energy is basically free source of energy, how good this energy is utilized in operating the desalination systems is considered in the gain output ratio (GOR) that allows for comparison of different systems comparison and shows the room for improvement.

Abstract: This chapter starts with a background about concentrating solar power systems and thermal energy storage systems and then a detailed literature review about concentrated solar power systems and supercritical Brayton carbon dioxide cycles. Next, a mathematical model was developed and presented which generates and optimizes a heliostat field effectively. This model was developed to demonstrate the optimization of a heliostat field using differential evolution, which is an evolutionary algorithm. The current model illustrates how to employ the developed model and its advantages. The optimization process calculates the optical performance parameters at every step of the optimization considering all the heliostats; thus yields accurate results as discussed in this chapter. On the other hand, complete mathematical model of supercritical CO2 Brayton cycles when integrated with solar thermal power tower system was presented and discussed.

Abstract: Heterogeneous semiconductor based photocatalytic hydrogen (H2) production by water splitting is one of the widely recognized promising sustainable technologies to deliver clean energy for future energy demands. The present review article mainly focus on the overview of principle of water splitting, different semiconductor nanomaterials used for photocatalytic water splitting in the presence of UV and solar light irradiation, role of sacrificial reagents, simultaneous degradation of pollutants and H2 production reaction, strategy for development of efficient photocatalyst for H2 production. Further the flaws associated with present photocatalytic system like recombination rate of electron–hole pairs, low visible-light response, use of hazardous irradiation sources and surface area of photocatalyst etc. has also been discussed. Recently the use of energy efficient light emitting diodes (LEDs) as an irradiation source for H2 production is highly attracted due to its unique characteristics. Recent literature on LED source based photocatalytic system for H2 production has also been summarized and highlighted. At last, the future prospects and challenges towards the designing of better photocatalytic system for H2 production have also been discussed. From the literature survey, it is concluded that construction of efficient photocatalytic system for simultaneous degradation of pollutants and H2 production under energy efficient irradiation source offer clean and simple system for solving the futuristic environmental concerns and energy crisis.